Truck drivers spend about 1800 hours per year resting in their cabs. In order to provide an environment suitable for resting and sleeping, the cabs are provided with heating and/or air conditioning units. Typically, drivers idle their truck engines while resting to provide power to operate the heating and air conditioning units. To idle such an engine for an extended period of time is an inefficient use of the engine and a waste of fuel.
For example, a typical on-highway truck burns approximately 0.6 to 0.9 gallons per hour while idling. Accordingly, fuel consumed during idling could be within the range of 1665 gallons per year. Further, the truck engines are designed and built to operate optimally at highway speeds. They may vibrate and cause uneven or undesired noise levels while idling. Additionally, extended idling may have negative effects on engine life.
Recently, federal and state governments began legislating new and higher standards for fuel emissions. Recognizing that the practice of idling while resting results in inefficient fuel consumption and additional emissions from the engine into the air, federal and state governments, along with industry, are looking for a solution to reduce truck idling during resting.
One system designed to reduce the need for truck idling during a rest period allows a truck operator to use an air conditioning or heating feature whether or not the engine is operating. This is accomplished by powering an HVAC system with a vehicle storage battery. While driving, the vehicle storage battery may be charged using a charging system. When the truck engine is shut down and the heating or air conditioning features are used, the HVAC draws energy from the storage battery.
Such a system, although an improvement over the prior art, still has many drawbacks. For example, as the energy level in the battery decreases, the HVAC may no longer be able to operate. Furthermore, such a system may direct energy generated by the engine to a recharger instead of providing the maximum amount of energy for driving the truck such as, for example, when a truck is going uphill and needs the maximum amount of energy.
The present invention addresses one or more of the deficiencies in the prior art.